Capacitive pressure sensors usually comprise a measuring diaphragm and a mating body, wherein the measuring diaphragm is connected to the mating body in a pressure-tight manner along a circumferential edge. A measuring chamber is formed between the mating body and the measuring diaphragm in which a reference pressure is present, and a pressure to be measured can be applied to an outside of the measuring diaphragm facing away from the measuring chamber. The measuring diaphragm can be deformed on the basis of the pressure, wherein the pressure sensor has a capacitive transducer having at least one mating body electrode and at least one diaphragm electrode. The capacity between the mating body electrode and the diaphragm electrode depends on the pressure-dependent deformation of the measuring diaphragm, and a central surface section of the measuring diaphragm in case of overload rests against the mating body with a resting surface area, the size of which is dependent on the pressure.
Due to its resting on the mating body, the measuring diaphragm is supported by an additional overload pressure range, which prevents the measuring diaphragm from reaching fracture stress. On the one hand, this protects the sensor against destruction, but on the other hand, a capacitive pressure measurement in a high pressure range is thus rendered impossible.
In order to enable this nonetheless, there is an option of increasing the distance between the measuring diaphragm and the mating body, which makes the measuring diaphragm rest on the mating body only when the pressure is higher. However, this is a disadvantage for two reasons. Firstly, with the increasing distance between the electrodes, the dC/dp dynamics decrease, and secondly, reaching fracture stress, and thus destroying the pressure sensor, becomes more likely. On the other hand, stiffer measuring diaphragms may be used, which in turn leads to loss of dC/dp dynamics.
However, measuring tasks are known in which low pressures must be measured with high precision during a vacuum process, wherein the prevailing steam pressure is to be captured in subsequent saturated steam sterilizations of the process plant. The latter may, if necessary, be completed with a lower measuring precision.